Method of sintering iron ore



June 18, 1963 J. R. @usr-:MAN ETAL METHOD oF sINTERiNG IRON ORE Filed March 10, 1959 fr maar/cnam rf rms/a4 Ys/sq. Fl:

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0M /aau 20M aw darm# mer/af .s/zf aF s/A/rm Fuz-z INVENTORS P15: 2 J/wfs A. ausm/AN ATTORNEY United States Patent O 3,094,408 METHOD OF SINTERING IRON ORE James R. Guseman, Perryopolis, and Thomas L. Myron,

Brentwood, Pa., assignors to United States Steel Corporation, a corporation of New Jersey Filed Mar. 10, 1959, Ser. No. 798,377 2 Claims. (Cl. 75-5) This invention relates to an improved iron oxide -sinter mix and method of sintering iron oxide.

An iron oxide sinter mix typically has a composition by weight on a dry basis about as follows:

Percent Iron ore fines 60 to 75 Sinter returns 20 to 40 Carbonaceous fuel 5 to 7 Moisture is added, whereby the mix feeding to a sintering machine has a moisture content about 1 to 2 percent greater than its natural moisture content. It is known that the top size of yfuel particles included in the mix should be about 1/8 to 1A inch, but as far as We are aware there has been no previous intent to limit the bottom size of fuel particles. The practice has been to luse yfuel with Whatever bottom size `of particle it happens to contain (usually inches).

An object of the present invention is to provide an improved iron oxide sinter mix and sintering method which attain signicant benefits by controlling the bottom size of fuel particles included in the mix.

A more specific object is to provide an improved iron oxide sinter mix -and sintering method `which require less fuel land also increase the capacity of a sintering machine by virtue of limiting the bottom size of fuel particles included in the In the drawing:

FIGURE l is a graph showing how sinter production varies with the fixed carbon content of sinter mix and with the bottom size of `fuel particles included in the mix; and

FIGURE 2 is another graph showing how sinter production varies With the bottom size of fuel particles at optimum iixed carbon content.

According to the present invention, we compound an iron oxide sinter mix of the usual ingredients (iron ore lines, sinter returns and carbonaceous fuel), but we limit the size of fuel particles to the range 1A: inch to 100 mesh, or preferably Ma inch to 20 mesh. In practice the `only step required to compound our mix, in addition to those required to compound a conventional mix, is to remove lines from the fuel, .preferably by screening the fuel on a 20 mesh screen. Fixed carbon is the effective component of fuel used in sinterinig; hence we express the fuel content of :sinter mix in terms of its yfixed carbon content. On a dry basis our sinter mix contains suflicient fuel to supply a fixed carbon content of about 3 to 4.5 percent or preferably about 3.5 percent, contrasted with -a iixed carbon content of about 3.5 to 5 percent required in a conventional sinter mix. `Our sinter mix includes ore fines and sinter returns in the usual proportions, and it can be moistened in the usual manner Iand burned on any suitable conventional sintering machine.

FIGURE 1 shows a series of curves in which the production rate of iinished sinter in tons per day per square foot of grate area is plotted against the xed carbon content of the mix :at different bottom size limits of fuel particles. The curves are the results of tests we conducted on a l5 inch square by l2 inch deep batch sintering unit. ln each instance our sinter mix consisted of minus 1A inch Venezuelan ore nes, Alpheus low-volatile bituminous coal sucient to supply the indicated lixed carbon content and having a top particle size of approximately 1A inch, and 25 percent minus 3A: inch sinter returns on a 3,094,408 Patented June 18, 1963 dry basis. We added sufficient moisture to produce a moisture content of 9 to 10 percent in Athe mix as fed to the sintering machine. The curves show `a progressively higher production rate as the bottom size of fuel particles increases to mesh and`20 mesh. The curves .also show that limiting the bottom size of fuel particles to 100 or 20 mesh lowers the optimum fixed carbon content from about 4.0 percent to about 3.5 percent.

.FIGURE 2 shows a curve in which the production rate of finished sinter in tons per day per square foot of grate area is plotted against the bottom particle size of fuel included in the mix, the absci-ssa being on a logarithmic scale. The iixed car-bon content of the mix was 3.5 percent, which we regard as optimum. This curve is a result of -tests similar to those from which We plotted the curves of FIGURE 1. The curve shows the produc-tion rate is highest when the bottom particle size of `fuel is about 20 mesh.

Following are specific examples which illustrate sinter mixes and sintering methods in laccordance with our invention. In each instance We mixed the materials on a conventional disc pelletizer, and fed the resulting mix to a 15 inch square by 12 Vinch deep batch sintering unit. We ignited the mix for l minute with a burner which covers the entire bed -with llame. We maintained a suction in the wind leg of the sintering unit equivalent to 30 inches of Water.

tumbler revolutions.

Example 2 Sinter fuel-Alpheus low-volatile coal:

Bottom size 20 mesh. Top size 1/s inch.

Composition of sinter mix: Percent 1A inch Venezuelan ore 70.3 Alpheus coal 4.7 -s inch sinter returns 25.0 -Fixed carbon content of sinter mix 3.5

Sinter test conditions:

Moisture content 12.5 .at the mixer. Position of returns -addition After mixing.

Test results:

Sintering time, 11.1 minutes. Peak wind-leg temperature, i1300 F. Net production rate, 4.2 tons per day per sq. ft. Sinter strength, 85.6% +3 mesh material after 25 tumbler revolutions.

Example 3 Sinter fuel- Alpheus low-volatile coal:

Bottom size 100 mesh. Top size 1A; inch.

' 3 Composition of sinter mix: Percent -lt inch Venezuelan ore 75.3 Alpheus coal 4.7 -3s inch sinter returns 20.() Fixed carbon content of sinter mix 3.5 Sinter test conditions:

Moisture content 12.0% at the mixer. Position of returns addition After mixing. Test results: Sintering time 121/2 minutes. Peak wind-leg temperature 810 F. Net production rate 3.2 tons per day per sq. ft.

Sinter-strength 90.0% +3 mesh material after 25 tumbler revolutions. Example/l Sinter fuel-Alpheus low-volatile coal:

Bottom size (approximately 7% -100 mesh material). Top size 1A; inch.

Composition of sinter mix: Percent l-1/1 inch Venezuelan ore 69.7 Alpheus coal 5.3 inch sinter returns 25.0 Fixed carbon content of sinter -mix 4.0

Sinter test conditions:

Moisture content 9.5% at the mixer.1 Position of `returns addition Before mixing. Test results:

Sintering time lminutes. Peak wind-leg'temperature 660 F. Net production rate 2.4 tons per day per sq. ft. Sinter strength 88.2% +3 mesh material after 25 turnbler revolutions.

1The different moisture content at the mixer is not significant. In Example 4, the sinter returns were added before the mixer, but in Iall four examples, the mix fed tto the sintering machine contained between 9 and 10 percent moisture.

We also obtained results similar to the foregoing with other carbonaceous fuels, namely coke breeze, anthracite fines, and char.

While we have shown and described certain preferred embodiments of the invention, it is apparent that other modifications may arise. Therefore, we do not Wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

l. An iron oxide sinter mix consisting of iron oxide fines and solid carbonaceous fuel particles proportioned to supply a xed carbon content on a dry basis of about 3 to 4.5% by Weight, said iron oxide fines being minus 1/1. inch and said fuel particles having a top size limit of about 1A; inch and a bottom size limit of about 20 mesh.

2, An iron oxide sinter mix consisting of the following by Weight on a dry basis:

-Mt inch iron ore fines-about to 75%,

sinter returnsabout 20 to 40%, and the balance carbonaceous fuel suiicient to supply a fixed carbon content of about 3 to 4.5

said fuel consisting of particles having a top size limit of about 1/8 inch and a bottom size limit of about 20 mesh.

References Cited in the file of this patent UNITED STATES PATENTS 2,858,204 Meyer et al. Oct. 28, 1953 2,861,881 Phelps Nov. 25, 1958 2,866,699l Weilandt et al. Dec. 30, 1958 OTHER REFERENCES Burns: Operation and Practice, Producing Iron Sinter at Ducktown and Copperliill, Tennessee, with Fine Flotation Sulphides; reprint for the Blast Furnace Coke Oven and Raw Materials Conf., Apr. 18-20, 1949. Published by Amer. Inst. of Mining and Met. Engineers, 29 W. 39th St., New York 18, -N.Y.; 5 pages.

English: Journal of Metals, February 1958, pages 122-124. 

1. AN IRON OXIDE SINTER MIX CONSISTING OF IRON OXIDE FINES AND SOLID CARBONACEOUS FUEL PARTICLES PROPORTIONED TO SUPPLY A FIXED CARBON CONTENT ON A DRY BASIS OF ABOUT 3 TO 4.5% BY WEIGHT, SAID OXIDE FINES BEING MINUS 